Diagnosis of diseases of the dental pulp can prove challenging to the dental practitioner. A tooth may appear normal in standard visual and radiographic examinations, and yet be undergoing a process of chronic degeneration. In other instances, a patient may experience tooth pain caused by acute inflammation of the pulp which later subsides without the necessity of endodontic therapy. As diagnostic tools are few and subjective, clinicians often must extract a tooth with no knowledge of its true pathological condition to avoid the possibility of future complications.
The techniques now employed to detect dental-pulp pathology are based on subjective evaluation of a patient's response to thermal, mechanical or electrical stimuli. A stimulus is applied to the tooth under examination and the patient is asked whether he or she feels a sensation. Problems with these techniques include: 1) the sensation can be unpleasant or painful to the patient, 2) successful stimulation of nerves in the pulp does not exclude the possibility of pulp disease; nerves can still respond even when blood circulation is impaired, 3) stimulating a tooth without also stimulating surrounding gingival tissues or nearby teeth is difficult and, therefore, false-positive errors are likely, and 4) no information concerning the degree or type of pulp pathology is provided because only complete devitalization can be positively identified.
Although various optical devices have been developed previously to assess the condition of teeth, none, as yet, has progressed beyond the prototype stage. Alfano, U.S. Pat. No. 4,290,433, discloses a method for caries detection based upon measurement of the relative luminescence of the tooth crown at two different wavelengths. Unlike the present invention which enables the determination of the condition of the tooth pulp, Alfano's invention only allows measurement of superficial abnormalities in the enamel and dentin layers which comprise the hard tissues of the tooth. Another U.S. patent issued to Hepp et al. identifies transillumination of the teeth and periodontal tissues as a potential diagnostic method, but as this method only allows detection of gross defects in the tooth crown or bony structures to which the teeth are attached, this method cannot be used to determine the conditions of tissue within the pulp cavity.
Maxwell and Webber have suggested a device for determination of tooth vitality based on the measurement of the volume of hemoglobin contained in the pulp cavity of a tooth. One deficiency of this device is its inability to determine vitality in a way that is independent of tooth size and shape. A large vital tooth with a small pulp cavity is likely to yield a different value from that of a small vital tooth containing a pulp cavity of equal volume. Thus, in general, only large changes in hemoglobin content occurring in the same tooth over time are discernible.